Well repairs,,, OUCH!!

[DarkBlack]

Your well setup falls in the middle of a Goulds 1hp pump as far as selecting head vs gpm.
Goulds 5hp motor alone is 70 lbs.
Putting on a "real" 5hp motor is just plain bad. Now you have a huge starting torque on a 1-1/2 hp pump mass. This means your torque tube is going to shift every time that huge motor starts, as it doesn't have an accompanying mass of pump bolted on, to resist rotation. Did they put on multiple torque tubes at least? If not, you'll be replacing broken wires or a split pipe after a couple years. Besides the extra $1k for the motor you had to change to oversized copper cables to prevent a voltage drop. Those aren't cheap. And lastly, If you're like me and want your mid sized portable generator to run your pump, forget it with your pump motor.
I see only drawbacks to a grossly oversized motor.

 

[SPIKER]

I would think the easiest solution now would be to use a VFD and drive the pump as a lower speed than across the line starting being done now.

Running slower will reduce flow rate of the system letting the well fill at a rate where it (PUMP) does not suck air.

Starting slower also will keep the piping from snapping off under the increased weight/torq load the big new pump makes. System should be set up so that the pump (VFD) turns on and runs slowly for small amount of time and can even run at full speed if needed but slow down as similar rate to keep from over torquing as it slows.

Mark

 

[4570Man]

I think a VFD has to have a 3 phase motor to work, but I am not sure about that.

 

[Professor Marvel]

VFDs are available for single phase motors now. In fact I have read here about VFD controlled well pumps. They apparently remove the pressure tank altogether.

 

[TheGoose]

I'm a lic water well pump installer here in tx. All pumps over 1.5 hp come separate from the motor. I can't really comment on matching a 5 hp motor to a 1.5 pump. You can always oversize the motor to any pump end. We don't have to set our pumps that deep here on the coast either.

 

[TheGoose]

Looking at the pump curve it looks like you're only pumping 6-9 gpm when you run out of water.

 

[westcliffe01]

I don't get the point of oversizing the motor. Surely the wear limit is the pumps ability to maintain flow against the substantial head + accumulator pressure ? A larger displacement pump with a bigger motor is just going to have a faster pump down rate. It could be that the OP's issue is that the water level in the aquifer has fallen and the pump will fail rapidly once it starts sucking air. Potentially just a matter of days to a few weeks before it is toast. In such a situation, installing a bigger pump and motor is exactly the wrong medicine.

When the well was originally drilled, the driller is supposed to determine the well flow rate and then size the pump/motor accordingly. It just sounds like the driller does not have the interest of the OP at heart in the choice of actions taken with this job. Or is simply not the brightest crayon in the box and does not take a methodical approach to problem solving.

 

[CurlyDave]

I would think the easiest solution now would be to use a VFD and drive the pump as a lower speed than across the line starting being done now.

Running slower will reduce flow rate of the system letting the well fill at a rate where it (PUMP) does not suck air.

Starting slower also will keep the piping from snapping off under the increased weight/torq load the big new pump makes. System should be set up so that the pump (VFD) turns on and runs slowly for small amount of time and can even run at full speed if needed but slow down as similar rate to keep from over torquing as it slows.

Mark

This is the most elegant (and least added expense) way to resolve the problem I have seen.

The guy who sold you the oversized motor is not your friend. I think it would be difficult to get him to admit he was trying to sell you the wrong equipment, but that is exactly what he did.

A cistern and a very low flow pump is really the way to go here. Then a second pump to pressurize the house.

You may not think you need a cistern, but the very low flow rate of this well is going to cause problems if you ever have a need for more water for a short time. What happens when you have house guests and 4 (or more) people want a shower in the morning instead of just 2? You really don't want to burn out your almost-new pump and motor when someone comes to visit.

 

[Larry Jones]

I suspect that that pump-motor combination is what the driller had available and wanted to get rid of it. I think a quick and cheap solution would be to add a gate valve in the line before it got to the tank and pressure switch. Then adjust the flow so it is a little less than the well recovery. Also, for home use I think the tank is way over sized, especially for a low flow well. Use a smaller tank so it will fill and shut off the pump so it won't be making long runs with the gate valve.

 

[DarkBlack]

VFDs are available for single phase motors now. In fact I have read here about VFD controlled well pumps. They apparently remove the pressure tank altogether.

I don't think so.
Show me a VFD designed to run an off the shelf 5HP single phase deep well pump. It makes no sense to me.
They do make drives for low starting torque small single phase motors, and they make 3 phase drives that can be powered by single phase.
If you want a variable speed 5hp well pump, you install a 3 phase motor. This is a high starting torque application.
Again, show a link to this. I say if you run an off the shelf single phase deep well pump at less than rated speed, you'll have a dead motor soon.
If it's new tech it must be really new. I'm gussing you're confusing a 3 phase vfd/motor combo powered by single phase.